The instant invention concerns an apparatus for the electroplating of chargeable mass elements in a cylindrical drum which rotates about its longitudinal axis, wherein said drum consists of its perforated, cylindrical cover, and its two end portions which are in vertical position to the rotational axis; whereby one of the end portions is irremovably fastened on the cylindrical drum cover serving as a cylinder base, and the other end portion is removably arranged as a cylinder cover for loading and unloading of the drum with the mass elements.
Such devices are generally utilized for electroplating relatively small amounts of very small mass elements, which exist mainly in the industries of electronics, watchmaking or jewelry-making. The mass elements to be treated appear mostly in small charge sizes, however, they are characterized by a very large variety of types and, due to often being very small of dimension, they require the drum to have fine perforations. The parts, for example transistors, may be of extreme sensitivity to mechanical damage. The various types of mass elements having varying charge sizes require drums with various capacities, as well as various rotational speeds (rate of revolutions), as well as various systems of cathodic contacting and last but not least varying perforations of the drum cylinder.
The prior art devices consist in general of a cylindrical drum member, which rotates between two supporting arms whereby said arms reach vertically into the electrolyte. The two support arms are provided with bearings to hold the drum. The bearing arms themselves are fastened at their upper ends to a frame, which rests on the cathode- or anode-rods of the shell which contains the electrolyte. The frame carries the electric driving motor, which is required for the rotational movements of the drum body. The rotational momentum is transmitted on the motor by means of a set of toothed wheels from the motor to the drum (driving pinion on the motor, interim wheel on one of the support arms and toothed wheel on a front side of the drum). The power which is required for the electroplating is received by the cathode rod via the frame and (generally by means of two cables which are placed through the two hollow spaces of the drum into the inside of the drum) is guided to the mass of elements which is to be plated.
The practice of electroplating very small mass elements forces the user to equip himself with a large number of various drum devices which characterize themselves predominantly by varying capacities of the individual drum cylinders, varying perforations of the cylinder covers, and varying cathodic contact systems in the drum. The required multitude of the varying drum apparati is expensive in procuring, maintaining, and is disadvantageous with regard to their practical handling (for performing the individual method-technical process steps in the series of the required solutions of treatment).
In prior art, devices are known which enable the exchanging of the drum cylinders fixed between the two support arms. The drum apparatus is thus divided into an apparatus (consisting substantially of the two support arms, the frame with the motor, the toothed wheel drive as well as the cathodic contact msystem) on one hand and the drum cylinder on the other hand. The apparatus fulfills exclusively the functions of holding and rotating the drum in its operational position, as well as conducting the electroplating current into the inside of the drum.
One of the prior art devices of the above-described type contains the control slits in the two support arms, through which are inserted the two pins of the drum cylinder in the operational position. One each bearing clip being pivotable about a clamping screw, arresting the associated bearing pin in its operational position. When one clamping screw is loosened, then the bearing clip can be tilted away around the clamping screw as point of rotational means, and the drum cylinder can be removed from the apparatus.
A further apparatus of this type proposes that one of the support arms is laterally folded away (by means of a hinge joint) and the drum cylinder can be inserted into or removed from the apparatus in an axial direction.
The above-discussed prior art devices, even though permitting the insertion of drums having varying perforations, under utilization of a single driving- and holding-aggregate, they do not however provide for the exchangeability of drums of varying capacities, which with a distance is the primary method-technical necessity. The prior art drum-apparati also do not consider the very large multiplicity of the mass elements which appear mostly in small character-sizes and must be plated separately according to their types.
There are furthermore devices known in the prior art which are clamped to the edge of the shell which contains the electrolyte. They are characterized by means of a very long shaft which is directed on a slant from the shell-edge (in general under an angle of about 45.degree. to the vertical) towards the bottom of the shell, below the lower end of which is fixedly attached a basket-like container for receiving the elements to be plated.
The axle of the shaft and the axle of the basket run coaxially and the shaft and basket are in synchronized rotation. The steep angle pitch of the basket has a result that only a small part of the capacity can be filled by the elements. The disadvantageous angle-pitch prevents an effective mixing of the elements, and consequently results in an uneven plating on the mass elements. In order to improve the uniformity of the electroplating, the number of elements in a batch must accordingly be reduced.